Resolves: fdo#39995 restore original semantics of GDIMetaFile::ReplaceAction

These semantics are fairly horrific, but existing code expects them, so
callers need to be changed if this is changed.

vcl/source/gdi/gdimtf.cxx

@@ -340,17 +340,14 @@ MetaAction* GDIMetaFile::NextAction()
 
 MetaAction* GDIMetaFile::ReplaceAction( MetaAction* pAction, size_t nAction )
 {
-    if ( nAction < aList.size() )
-    {
-        ::std::vector< MetaAction* >::iterator it = aList.begin();
-        ::std::advance( it, nAction );
-        (*it)->Delete();
-        *it = pAction;
-    }
+    if ( nAction >= aList.size() )
+        return NULL;
+    //fdo#39995 This does't increment the incoming action ref-count nor does it
+    //decrement the outgoing action ref-count
+    std::swap(pAction, aList[nAction]);
     return pAction;
 }
 
-
 // ------------------------------------------------------------------------
 
 GDIMetaFile& GDIMetaFile::operator=( const GDIMetaFile& rMtf )